Many professions require that a person be exposed to high ambient temperatures for sustained periods of time while wearing protective garments. At the same time, they must be free to move about over large distances. Hence there is a need for a portable personal cooling apparatus that does not unduly restrict a person's movements or compromise his or her ability to wear other protective garments.
An example is a fire fighter. The fire fighter must enter buildings with high ambient temperatures with protective outer garments on. The firefighter must also be free to move about the building and may have a high exertion rate. He or she may, for example, be producing 500 thermal watts of heat simply by virtue of his or her exertion. This heat needs to be dissipated to an environment that may locally have a temperature of 120 degrees F. or more and have a high humidity. Hence normal cooling of the body through evaporation of perspiration is not effective. If this heat is not dissipated, then the firefighter may suffer heat stroke.
Similarly, combat soldiers stationed in warm climates may also need to have a means for dissipating internally generated body heat when they are wearing body armor. The body armor may inhibit a soldier's normal ability to dissipate heat through evaporation.